text: /****************************************************************************
   * fs/vfs/fs_timerfd.c
   *
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.  The
   * ASF licenses this file to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance with the
   * License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
   * License for the specific language governing permissions and limitations
   * under the License.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  #include <stdio.h>
  #include <poll.h>
  #include <assert.h>
  #include <errno.h>
  #include <fcntl.h>
  
  #include <debug.h>
  
  #include <nuttx/wdog.h>
  #include <nuttx/wqueue.h>
  #include <nuttx/spinlock.h>
  
  #include <sys/ioctl.h>
  #include <sys/timerfd.h>
  
  #include "clock/clock.h"
  #include "inode/inode.h"
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  #define TIMER_FD_WORK LPWORK
  
  /****************************************************************************
   * Private Types
   ****************************************************************************/
  
  typedef struct timerfd_waiter_sem_s
  {
    sem_t sem;
    struct timerfd_waiter_sem_s *next;
  } timerfd_waiter_sem_t;
  
  /* This structure describes the internal state of the driver */
  
  struct timerfd_priv_s
  {
    sem_t         exclsem;        /* Enforces device exclusive access */
    timerfd_waiter_sem_t *rdsems; /* List of blocking readers */
    int           clock;          /* Clock to use as the timing base */
    int           delay;          /* If non-zero, used to reset repetitive
                                   * timers */
    struct wdog_s wdog;           /* The watchdog that provides the timing */
    struct work_s work;           /* For deferred timeout operations */
    timerfd_t     counter;        /* timerfd counter */
    spinlock_t    lock;           /* timerfd counter specific lock */
    unsigned int  minor;          /* timerfd minor number */
    uint8_t       crefs;          /* References counts on timerfd (max: 255) */
  
    /* The following is a list if poll structures of threads waiting for
     * driver events.
     */
  
  #ifdef CONFIG_TIMER_FD_POLL
    FAR struct pollfd *fds[CONFIG_TIMER_FD_NPOLLWAITERS];
  #endif
  };
  
  /****************************************************************************
   * Private Function Prototypes
   ****************************************************************************/
  
  static int timerfd_open(FAR struct file *filep);
  static int timerfd_close(FAR struct file *filep);
  
  static ssize_t timerfd_read(FAR struct file *filep, FAR char *buffer,
                              size_t len);
  #ifdef CONFIG_TIMER_FD_POLL
  static int timerfd_poll(FAR struct file *filep, FAR struct pollfd *fds,
                          bool setup);
  
  static void timerfd_pollnotify(FAR struct timerfd_priv_s *dev,
                                 pollevent_t eventset);
  #endif
  
  static int timerfd_blocking_io(FAR struct timerfd_priv_s *dev,
                                 timerfd_waiter_sem_t *sem,
                                 FAR timerfd_waiter_sem_t **slist);
  
  static unsigned int timerfd_get_unique_minor(void);
  static void timerfd_release_minor(unsigned int minor);
  
  static FAR struct timerfd_priv_s *timerfd_allocdev(void);
  static void timerfd_destroy(FAR struct timerfd_priv_s *dev);
  
  static void timerfd_timeout_work(FAR void *arg);
  static void timerfd_timeout(wdparm_t idev);
  
  /****************************************************************************
   * Private Data
   ****************************************************************************/
  
  static const struct file_operations g_timerfd_fops =
  {
    timerfd_open,  /* open */
    timerfd_close, /* close */
    timerfd_read,  /* read */
    NULL,          /* write */
    NULL,          /* seek */
    NULL,          /* ioctl */
  #ifdef CONFIG_TIMER_FD_POLL
    timerfd_poll   /* poll */
  #else
    NULL           /* poll */
  #endif
  #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
    , NULL         /* unlink */
  #endif
  };
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  static FAR struct timerfd_priv_s *timerfd_allocdev(void)
  {
    FAR struct timerfd_priv_s *dev;
  
    dev = (FAR struct timerfd_priv_s *)
      kmm_zalloc(sizeof(struct timerfd_priv_s));
    if (dev)
      {
        /* Initialize the private structure */
  
        nxsem_init(&dev->exclsem, 0, 0);
      }
  
    return dev;
  }
  
  static void timerfd_destroy(FAR struct timerfd_priv_s *dev)
  {
    wd_cancel(&dev->wdog);
    work_cancel(TIMER_FD_WORK, &dev->work);
    nxsem_destroy(&dev->exclsem);
    kmm_free(dev);
  }
  
  static timerfd_t timerfd_get_counter(FAR struct timerfd_priv_s *dev)
  {
    timerfd_t counter;
    irqstate_t intflags;
  
    intflags = spin_lock_irqsave(&dev->lock);
    counter = dev->counter;
    spin_unlock_irqrestore(&dev->lock, intflags);
  
    return counter;
  }
  
  #ifdef CONFIG_TIMER_FD_POLL
  static void timerfd_pollnotify(FAR struct timerfd_priv_s *dev,
                                 pollevent_t eventset)
  {
    FAR struct pollfd *fds;
    int i;
  
    for (i = 0; i < CONFIG_TIMER_FD_NPOLLWAITERS; i++)
      {
        fds = dev->fds[i];
        if (fds)
          {
            fds->revents |= eventset & fds->events;
  
            if (fds->revents != 0)
              {
                nxsem_post(fds->sem);
              }
          }
      }
  }
  #endif
  
  static unsigned int timerfd_get_unique_minor(void)
  {
    static unsigned int minor;
  
    return minor++;
  }
  
  static void timerfd_release_minor(unsigned int minor)
  {
  }
  
  static int timerfd_open(FAR struct file *filep)
  {
    FAR struct inode *inode = filep->f_inode;
    FAR struct timerfd_priv_s *priv = inode->i_private;
    int ret;
  
    /* Get exclusive access to the device structures */
  
    ret = nxsem_wait(&priv->exclsem);
    if (ret < 0)
      {
        return ret;
      }
  
    finfo("crefs: %d <%s>\n", priv->crefs, inode->i_name);
  
    if (priv->crefs >= 255)
      {
        /* More than 255 opens; uint8_t would overflow to zero */
  
        ret = -EMFILE;
      }
    else
      {
        /* Save the new open count on success */
  
        priv->crefs += 1;
        ret = OK;
      }
  
    nxsem_post(&priv->exclsem);
    return ret;
  }
  
  static int timerfd_close(FAR struct file *filep)
  {
    int ret;
    FAR struct inode *inode = filep->f_inode;
    FAR struct timerfd_priv_s *priv = inode->i_private;
  
    /* devpath: TIMER_FD_VFS_PATH + /tfd (4) + %u (10) + null char (1) */
  
    char devpath[sizeof(CONFIG_TIMER_FD_VFS_PATH) + 4 + 10 + 1];
  
    /* Get exclusive access to the device structures */
  
    ret = nxsem_wait(&priv->exclsem);
    if (ret < 0)
      {
        return ret;
      }
  
    finfo("crefs: %d <%s>\n", priv->crefs, inode->i_name);
  
    /* Decrement the references to the driver.  If the reference count will
     * decrement to 0, then uninitialize the driver.
     */
  
    if (priv->crefs > 1)
      {
        /* Just decrement the reference count and release the semaphore */
  
        priv->crefs--;
        nxsem_post(&priv->exclsem);
        return OK;
      }
  
    /* Re-create the path to the driver. */
  
    finfo("destroy\n");
    sprintf(devpath, CONFIG_TIMER_FD_VFS_PATH "/tfd%u", priv->minor);
  
    /* Will be unregistered later after close is done */
  
    unregister_driver(devpath);
  
    DEBUGASSERT(priv->exclsem.semcount == 0);
    timerfd_release_minor(priv->minor);
    timerfd_destroy(priv);
  
    return OK;
  }
  
  static int timerfd_blocking_io(FAR struct timerfd_priv_s *dev,
                                 timerfd_waiter_sem_t *sem,
                                 FAR timerfd_waiter_sem_t **slist)
  {
    int ret;
    sem->next = *slist;
    *slist = sem;
  
    nxsem_post(&dev->exclsem);
  
    /* Wait for timerfd to notify */
  
    ret = nxsem_wait(&sem->sem);
  
    if (ret < 0)
      {
        /* Interrupted wait, unregister semaphore
         * TODO ensure that exclsem wait does not fail (ECANCELED)
         */
  
        nxsem_wait_uninterruptible(&dev->exclsem);
  
        timerfd_waiter_sem_t *cur_sem = *slist;
  
        if (cur_sem == sem)
          {
            *slist = sem->next;
          }
        else
          {
            while (cur_sem)
              {
                if (cur_sem->next == sem)
                  {
                    cur_sem->next = sem->next;
                    break;
                  }
              }
          }
  
        nxsem_post(&dev->exclsem);
        return ret;
      }
  
    return nxsem_wait(&dev->exclsem);
  }
  
  static ssize_t timerfd_read(FAR struct file *filep, FAR char *buffer,
                              size_t len)
  {
    FAR struct inode *inode = filep->f_inode;
    FAR struct timerfd_priv_s *dev = inode->i_private;
    irqstate_t intflags;
    ssize_t ret;
  
    if (len < sizeof(timerfd_t) || buffer == NULL)
      {
        return -EINVAL;
      }
  
    ret = nxsem_wait(&dev->exclsem);
    if (ret < 0)
      {
        return ret;
      }
  
    /* Wait for an incoming event */
  
    if (timerfd_get_counter(dev) == 0)
      {
        if (filep->f_oflags & O_NONBLOCK)
          {
            nxsem_post(&dev->exclsem);
            return -EAGAIN;
          }
  
        timerfd_waiter_sem_t sem;
        nxsem_init(&sem.sem, 0, 0);
        nxsem_set_protocol(&sem.sem, SEM_PRIO_NONE);
  
        do
          {
            ret = timerfd_blocking_io(dev, &sem, &dev->rdsems);
            if (ret < 0)
              {
                nxsem_destroy(&sem.sem);
                return ret;
              }
          }
        while (timerfd_get_counter(dev) == 0);
  
        nxsem_destroy(&sem.sem);
      }
  
    /* Device ready for read.  Ensure that interrupts are disabled and we
     * do not lose counts if expiration occurs after read, but before setting
     * counter to zero
     */
  
    intflags = spin_lock_irqsave(&dev->lock);
  
    *(FAR timerfd_t *)buffer = dev->counter;
    dev->counter = 0;
  
    spin_unlock_irqrestore(&dev->lock, intflags);
  
    nxsem_post(&dev->exclsem);
    return sizeof(timerfd_t);
  }
  
  #ifdef CONFIG_TIMER_FD_POLL
  static int timerfd_poll(FAR struct file *filep, FAR struct pollfd *fds,
                          bool setup)
  {
    FAR struct inode *inode = filep->f_inode;
    FAR struct timerfd_priv_s *dev = inode->i_private;
    int ret;
    int i;
  
    ret = nxsem_wait(&dev->exclsem);
    if (ret < 0)
      {
        return ret;
      }
  
    ret = OK;
  
    if (!setup)
      {
        /* This is a request to tear down the poll. */
  
        FAR struct pollfd **slot = (FAR struct pollfd **)fds->priv;
  
        /* Remove all memory of the poll setup */
  
        *slot                = NULL;
        fds->priv            = NULL;
        goto out;
      }
  
    /* This is a request to set up the poll. Find an available
     * slot for the poll structure reference
     */
  
    for (i = 0; i < CONFIG_TIMER_FD_NPOLLWAITERS; i++)
      {
        /* Find an available slot */
  
        if (!dev->fds[i])
          {
            /* Bind the poll structure and this slot */
  
            dev->fds[i] = fds;
            fds->priv   = &dev->fds[i];
            break;
          }
      }
  
    if (i >= CONFIG_TIMER_FD_NPOLLWAITERS)
      {
        fds->priv = NULL;
        ret       = -EBUSY;
        goto out;
      }
  
    /* Notify the POLLIN event if the counter is not zero */
  
    if (timerfd_get_counter(dev) > 0)
      {
        timerfd_pollnotify(dev, POLLIN);
      }
  
  out:
    nxsem_post(&dev->exclsem);
    return ret;
  }
  #endif
  
  static void timerfd_timeout_work(FAR void *arg)
  {
    FAR struct timerfd_priv_s *dev = (FAR struct timerfd_priv_s *)arg;
    int ret;
  
    ret = nxsem_wait_uninterruptible(&dev->exclsem);
    if (ret < 0)
      {
        wd_cancel(&dev->wdog);
        return;
      }
  
  #ifdef CONFIG_TIMER_FD_POLL
    /* Notify all poll/select waiters */
  
    timerfd_pollnotify(dev, POLLIN);
  #endif
  
    /* Notify all of the waiting readers */
  
    timerfd_waiter_sem_t *cur_sem = dev->rdsems;
    while (cur_sem != NULL)
      {
        nxsem_post(&cur_sem->sem);
        cur_sem = cur_sem->next;
      }
  
    dev->rdsems = NULL;
  
    nxsem_post(&dev->exclsem);
  }
  
  static void timerfd_timeout(wdparm_t idev)
  {
    FAR struct timerfd_priv_s *dev = (FAR struct timerfd_priv_s *)idev;
    irqstate_t intflags;
  
    /* Disable interrupts to ensure that expiration counter is accessed
     * atomically
     */
  
    intflags = spin_lock_irqsave(&dev->lock);
  
    /* Increment timer expiration counter */
  
    dev->counter++;
  
    work_queue(TIMER_FD_WORK, &dev->work, timerfd_timeout_work, dev, 0);
  
    /* If this is a repetitive timer, then restart the watchdog */
  
    if (dev->delay)
      {
        wd_start(&dev->wdog, dev->delay, timerfd_timeout, idev);
      }
  
    spin_unlock_irqrestore(&dev->lock, intflags);
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  int timerfd_create(int clockid, int flags)
  {
    FAR struct timerfd_priv_s *new_dev;
    int new_fd;
    int ret;
  
    /* Sanity checks. */
  
    if (clockid != CLOCK_REALTIME
  #ifdef CONFIG_CLOCK_MONOTONIC
        && clockid != CLOCK_MONOTONIC
        && clockid != CLOCK_BOOTTIME
  #endif /* CONFIG_CLOCK_MONOTONIC */
        )
      {
        ret = -EINVAL;
        goto errout;
      }
  
    /* devpath: TIMER_FD_VFS_PATH + /tfd (4) + %u (10) + null char (1) */
  
    char devpath[sizeof(CONFIG_TIMER_FD_VFS_PATH) + 4 + 10 + 1];
  
    /* Allocate instance data for this driver */
  
    new_dev = timerfd_allocdev();
    if (new_dev == NULL)
      {
        /* Failed to allocate new device */
  
        ret = -ENOMEM;
        goto errout;
      }
  
    /* Initialize the timer instance */
  
    new_dev->clock = clockid;
    new_dev->crefs = 1;
    new_dev->delay = 0;
    new_dev->counter = 0;
  
    /* Request a unique minor device number */
  
    new_dev->minor = timerfd_get_unique_minor();
  
    /* Get device path */
  
    sprintf(devpath, CONFIG_TIMER_FD_VFS_PATH "/tfd%u", new_dev->minor);
  
    /* Register the driver */
  
    ret = register_driver(devpath, &g_timerfd_fops, 0444, new_dev);
    if (ret < 0)
      {
        ferr("Failed to register new device %s: %d\n", devpath, ret);
        ret = -ENODEV;
        goto errout_release_minor;
      }
  
    /* Device is ready for use */
  
    nxsem_post(&new_dev->exclsem);
  
    /* Try open new device */
  
    new_fd = nx_open(devpath, O_RDONLY |
                     (flags & (TFD_NONBLOCK | TFD_CLOEXEC)));
  
    if (new_fd < 0)
      {
        ret = new_fd;
        goto errout_unregister_driver;
      }
  
    return new_fd;
  
  errout_unregister_driver:
    unregister_driver(devpath);
  errout_release_minor:
    timerfd_release_minor(new_dev->minor);
    timerfd_destroy(new_dev);
  errout:
    set_errno(-ret);
    return ERROR;
  }
  
  int timerfd_settime(int fd, int flags,
                      FAR const struct itimerspec *new_value,
                      FAR struct itimerspec *old_value)
  {
    FAR struct file *filep;
    FAR struct timerfd_priv_s *dev;
    irqstate_t intflags;
    sclock_t delay;
    int ret;
  
    /* Some sanity checks */
  
    if (!new_value)
      {
        ret = -EFAULT;
        goto errout;
      }
  
    if (flags && (flags & TFD_TIMER_ABSTIME) == 0)
      {
        ret = -EINVAL;
        goto errout;
      }
  
    /* Get file pointer by file descriptor */
  
    ret = fs_getfilep(fd, &filep);
    if (ret < 0)
      {
        goto errout;
      }
  
    /* Check fd come from us */
  
    if (!filep->f_inode || filep->f_inode->u.i_ops != &g_timerfd_fops)
      {
        ret = -EINVAL;
        goto errout;
      }
  
    dev = (FAR struct timerfd_priv_s *)filep->f_inode->i_private;
  
    if (old_value)
      {
        /* Get the number of ticks before the underlying watchdog expires */
  
        delay = wd_gettime(&dev->wdog);
  
        /* Convert that to a struct timespec and return it */
  
        clock_ticks2time(delay, &old_value->it_value);
        clock_ticks2time(dev->delay, &old_value->it_interval);
      }
  
    /* Disable interrupts here to ensure that expiration counter is accessed
     * atomicaly and timeout work is canceled with the same sequence
     */
  
    intflags = spin_lock_irqsave(&dev->lock);
  
    /* Disarm the timer (in case the timer was already armed when
     * timerfd_settime() is called).
     */
  
    wd_cancel(&dev->wdog);
  
    /* Cancel notification work */
  
    work_cancel(TIMER_FD_WORK, &dev->work);
  
    /* Clear expiration counter */
  
    dev->counter = 0;
  
    /* If the it_value member of value is zero, the timer will not be
     * re-armed
     */
  
    if (new_value->it_value.tv_sec <= 0 && new_value->it_value.tv_nsec <= 0)
      {
        spin_unlock_irqrestore(NULL, intflags);
        return OK;
      }
  
    /* Setup up any repetitive timer */
  
    if (new_value->it_interval.tv_sec > 0 ||
        new_value->it_interval.tv_nsec > 0)
      {
        clock_time2ticks(&new_value->it_interval, &delay);
  
        /* REVISIT: Should delay be sclock_t? */
  
        dev->delay = (int)delay;
      }
    else
      {
        dev->delay = 0;
      }
  
    /* We need to disable timer interrupts through the following section so
     * that the system timer is stable.
     */
  
    /* Check if abstime is selected */
  
    if ((flags & TFD_TIMER_ABSTIME) != 0)
      {
        /* Calculate a delay corresponding to the absolute time in 'value' */
  
        clock_abstime2ticks(dev->clock, &new_value->it_value, &delay);
      }
    else
      {
        /* Calculate a delay assuming that 'value' holds the relative time
         * to wait.  We have internal knowledge that clock_time2ticks always
         * returns success.
         */
  
        clock_time2ticks(&new_value->it_value, &delay);
      }
  
    /* If the time is in the past or now, then set up the next interval
     * instead (assuming a repetitive timer).
     */
  
    if (delay <= 0)
      {
        delay = dev->delay;
      }
  
    /* Then start the watchdog */
  
    if (delay > 0)
      {
        ret = wd_start(&dev->wdog, delay, timerfd_timeout, (wdparm_t)dev);
        if (ret < 0)
          {
            spin_unlock_irqrestore(&dev->lock, intflags);
            goto errout;
          }
      }
  
    spin_unlock_irqrestore(&dev->lock, intflags);
    return OK;
  
  errout:
    set_errno(-ret);
    return ERROR;
  }
  
  int timerfd_gettime(int fd, FAR struct itimerspec *curr_value)
  {
    FAR struct file *filep;
    FAR struct timerfd_priv_s *dev;
    sclock_t ticks;
    int ret;
  
    /* Some sanity checks */
  
    if (!curr_value)
      {
        ret = -EFAULT;
        goto errout;
      }
  
    /* Get file pointer by file descriptor */
  
    ret = fs_getfilep(fd, &filep);
    if (ret < 0)
      {
        goto errout;
      }
  
    /* Check fd come from us */
  
    if (!filep->f_inode || filep->f_inode->u.i_ops != &g_timerfd_fops)
      {
        ret = -EINVAL;
        goto errout;
      }
  
    dev = (FAR struct timerfd_priv_s *)filep->f_inode->i_private;
  
    /* Get the number of ticks before the underlying watchdog expires */
  
    ticks = wd_gettime(&dev->wdog);
  
    /* Convert that to a struct timespec and return it */
  
    clock_ticks2time(ticks, &curr_value->it_value);
    clock_ticks2time(dev->delay, &curr_value->it_interval);
    return OK;
  
  errout:
    set_errno(-ret);
    return ERROR;
  }
  